Methods for improving dimensional stability and/or durable press properties of elastic fabrics and elastic fabrics with improved properties

ABSTRACT

Methods for providing elastic fabric comprising synthetic elastic fibers and natural fibers with improved dimensional stability or improved durable press while maintaining stretch recovery properties comprise treating the fabric with a treatment composition comprising formaldehyde and a catalyst for crosslinking the formaldehyde with natural fibers in the fabric, and processing the treated fabric to effect crosslinking of the formaldehyde and to maintain stretch performance properties. Fabrics comprising synthetic elastic fibers and natural fibers exhibiting improved dimensional stability and/or durable press properties in combination with additional advantageous properties are produced.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Application Serial No. 60/389,413, filed Jun. 17, 2003.

FIELD OF THE INVENTION

[0002] This invention relates to methods for providing elastic fabricscomprising synthetic elastic fibers and natural fibers and havingimproved dimensional stability and/or durable press properties,particularly while maintaining good stretch recovery of the fabrics.This invention also relates to elastic fabrics which have improveddimensional stability and/or improved durable press properties,particularly wherein the fabrics comprise synthetic elastic fibers andnatural fibers.

BACKGROUND OF THE INVENTION

[0003] Many fabrics, comprising natural fibers do not possess durablepress (or “wash and wear” or “smooth-dry”) performance or dimensionalstability, i.e., shrinkage resistance. Cellulosic fabrics, such asfabrics containing cotton, for instance, have been treated withaminoplast resins, including N-methylol cross-linking resins such asdimethylol dihydroxyethyleneurea (DMDHEU) or dimethylol propylcarbamate(DMPC), to impart durable press properties, as disclosed, for example,in the Martin et al U.S. Pat. No. 4,521,176. Unfortunately, many reactedaminoplast resins break down during storage, thus releasingformaldehyde. The formaldehyde release may occur not only throughout thepreparation of the fabric but also during garment-making. Further,garments or fabrics treated with aminoplast resins may releaseadditional formaldehyde when stored under humid conditions. Aminoplastresins may also hydrolyze during washing procedures, resulting in a lossof the durable press performance. Additionally, aminoplast resins tendto give fabric a harsher handle, that is, make the fabric feel lesssoft. As the resins make the fabric feel less soft, the fabric must betreated with additional softeners, for example silicone softeners.Unfortunately, the silicone softeners tend to make the fabrichydrophobic although it is often preferred that the fabric havehydrophilic properties.

[0004] Cellulosic fibers have also been cross-linked with formaldehydeto impart durable press properties. For example, the Payet U.S. Pat.Nos. 3,960,482, 3,960,483, 4,067,688 and 4,104,022 disclose durablepress processes which comprise impregnating a cellulosicfiber-containing fabric with an aqueous solution comprising a catalyst,and, while the fabric has a moisture content of above 20% by weight,exposing the fabric to formaldehyde vapors and curing under conditionsat which formaldehyde reacts with the cellulose. The Payet U.S. Pat. No.4,108,598 discloses a process which comprises treating cellulosicfiber-containing fabrics with an aqueous solution of formaldehyde and acatalyst, heat curing the treated fabric by introducing the fabric intoa heating zone, and gradually increasing the temperature of the heatingzone, thereby increasing the temperature of the heated fabric to preventthe loss of an amount of formaldehyde which will reduce the overallextent of curing. The Payet U.S. Pat. No. 5,885,303 also discloses adurable press process for cellulosic fiber-containing fabrics. Theprocess comprises treating the fabric with an aqueous solution offormaldehyde, a catalyst capable of catalyzing the cross-linkingreaction between formaldehyde and cellulose, and an effective amount ofa silicone elastomer to reduce loss in tear strength in the treatedfabric. Formaldehyde is generally less expensive than aminoplast resins,and formaldehyde treatment of cellulosic fabrics typically results indurable press properties which are more durable than those obtained byaminoplast resins.

[0005] Many consumers also prefer garments containing synthetic elasticfibers and/or garments comprising a blend of synthetic elastic fibersand natural fibers such as, for instance, spandex blend knit and/orwoven fabrics. Fabrics containing synthetic elastic fibers have theability to be stretched repeatedly and still recover to very near theiroriginal length and/or shape. Such fabrics are often incorporated ingarments which comfortably conform to the consumer's body withoutbagging and/or sagging. However, these fabrics often undesirably exhibitnoticeable shrinking and/or wrinkling after aqueous laundering, and itis difficult to find means for overcoming the disadvantages whilemaintaining the desirable elastic properties of such fabrics.Additionally, the life expectancy of garments made of these fabrics isoften decreased by repeated heat treatments used during manufacturingand/or home care procedures, as combinations of heat and tensionaccelerate the fabric growth of elastic fabrics thereby resulting in anunacceptable fit and/or appearance.

[0006] Accordingly, there is a continuing need to further improveindividual characteristics of elastic fabrics containing a blend ofsynthetic elastic fibers and natural fibers and to improve the overallcombinations of properties exhibited by such fabrics.

SUMMARY OF THE INVENTION

[0007] Accordingly, it is an object of the present invention to obviateproblems of the prior art. It is a further object of the presentinvention to provide methods for improving the dimensional stabilityand/or durable press properties of fabrics and particularly to improvethe dimensional stability and/or durable press properties of elasticfabrics containing synthetic elastic fibers and natural fibers, whilemaintaining stretch recovery of the fabrics. It is a related object toprovide methods for preparing elastic fabrics which exhibit advantageouscombinations of properties and which are suitable for aqueous washing orlaundering, and to provide elastic fabrics exhibiting such advantageousproperties.

[0008] These and additional objects are provided by the methods andfabrics of the invention. In one embodiment, the invention is directedto methods for providing elastic fabric comprising synthetic elasticfibers and natural fibers with improved dimensional stability whilemaintaining stretch recovery properties of the fabric. The methodscomprise treating elastic fabric comprising synthetic elastic fibers andnatural fibers with a treatment composition comprising formaldehyde, anda catalyst for crosslinking the formaldehyde with natural fibers in thefabric, and processing the treated fabric to effect crosslinking of theformaldehyde and to maintain stretch performance properties. Accordingto more specific embodiments, the treated fabrics are processed undercontrolled conditions such as, for instance, temperature, time andtension levels.

[0009] In another embodiment, the invention is directed to methods forproviding elastic fabric comprising synthetic elastic fibers and naturalfibers with improved durable press while maintaining stretch recoveryproperties of the fabric. The methods comprise treating elastic fabriccomprising synthetic elastic fibers and natural fibers with a treatmentcomposition comprising formaldehyde and a catalyst for crosslinking theformaldehyde with natural fibers in the fabric, and processing thetreated fabric to effect crosslinking of the formaldehyde and tomaintain stretch performance properties. According to more specificembodiments, the treated fabrics are processed under controlledconditions such as, for instance, temperature, time and tension levels.

[0010] In yet additional embodiments, the invention is directed tofabric comprising synthetic elastic fibers and natural fibers andexhibiting a durable press value of at least about 3.0 after the fabrichas been aqueous laundered one time, and to fabric comprising syntheticelastic fibers and natural fibers and exhibiting a length dimensionalchange and a width dimensional change of less than about 5% each afterthe fabric has been aqueous laundered one time.

[0011] The methods of the invention are advantageous in providingfabrics which exhibit improved dimensional stability and/or durablepress properties, while maintaining stretch recovery properties.

[0012] These and additional aspects, objects and advantages of theinvention are more fully described in the detailed description.

DETAILED DESCRIPTION

[0013] The present invention is directed to methods for providingfabrics, particularly elastic fabrics comprising synthetic elasticfibers and natural fibers, with improved dimensional stability and/orgood durable press properties while maintaining stretch recoveryproperties. This invention also relates to elastic fabrics comprisingsynthetic elastic fibers and natural fibers and exhibiting good durablepress and/or dimensional stability even after aqueous laundering.

[0014] As used herein, “dimensional stability” refers generally to theability of a fabric to resist dimensional change, particularly afteraqueous laundering. As employed in the present invention, improveddimensional stability indicates that the fabric exhibits a dimensionalchange in length and width, after the fabric has been aqueous launderedone time, less than that exhibited by the untreated fabric after oneaqueous laundering.

[0015] As used herein, “stretch recovery” refers generally to theability of a fabric to substantially recover to very near its originallength and/or shape after being stretched, particularly such that thefabric does not retain a permanent deformation. As used herein,“permanent deformation” refers generally to the ability of a fabric toretain a permanent length and/or shape after being stretched such thatthe fabric does not recover back to or near the original fabricdimensions exhibited prior to stretching the fabric. In one embodiment,the resulting fabrics according to the present invention exhibit afabric growth of not greater than about 5% after the fabric has beenstretched at least about 80% of its maximum stretch under a four poundload according to ASTM D 3107. As used herein, “fabric stretch” refersgenerally to the increase in length of a specimen of fabric resultingfrom a load applied under specified conditions (specified tension) and“fabric growth” refers generally to the difference between the originallength of a specimen and its length after application of a specifiedtension for a prescribed time and the subsequent removal of the tension.

[0016] The fabrics employed in the present invention comprise syntheticelastic fibers and natural fibers. As used herein, “fiber” refersgenerally to a generic term for any one of the various types of matterthat form the basic elements of a textile and that is characterized byhaving a length at least 100 times greater than its diameter. As usedherein, “filament” refers generally to a continuous fiber of extremelylong length, whereas a “staple” refers generally to a natural fiber ofcut lengths from a filament and “tow”, refers to a coarse and/or brokenfiber and/or filament.

[0017] As used herein, “yam” refers to a continuous strand of textilefibers, generally filaments, and/or materials in a form suitable forknitting, weaving or otherwise intertwining for a textile fabric. Asused herein, “fabrics” generally refer to knitted fabrics, wovenfabrics, or non-woven fabrics prepared from yarns or fibers, while“garments” generally refer to wearable articles comprising fabrics,including, but not limited to, shirts, blouses, dresses, pants, sweatersand coats. Non-woven fabrics include textile structures produced bybonding or interlocking of fibers, or both, accomplished by amechanical, chemical, thermal, or solvent means and combinationsthereof. “Textiles”, includes fabrics, yarns, and articles comprisingfabrics and/or yarns, such as garments, home goods, including, but notlimited to, bed and table linens, draperies and curtains, andupholsteries, and the like.

[0018] As used herein, “natural fibers” refer to fibers which areobtained from natural sources, such as cellulosic fibers and proteinfibers, or which are formed by the regeneration of or processing ofnatural occurring fibers and/or products. Natural fibers are notintended to include fibers formed from petroleum products. Naturalfibers include fibers formed from cellulose, such as cotton fiber andregenerated cellulose fiber, commonly referred to as rayon, or acetatefiber derived by reacting cellulose with acetic acid and aceticanhydride in the presence of sulfuric acid. As used herein, “naturalfibers”, are intended to include natural fibers in any form, includingindividual filaments, and fibers present in yarns, fabrics and othertextiles, while “individual natural fibers” is intended to refer toindividual natural filaments.

[0019] As used herein, “thermoplastic fiber” refers generally to a classname for various genera of filament, tow, or staple produced from afiber forming substance which is synthesized from a chemical compound.

[0020] As used herein, “cellulosic fibers” are intended to refer tofibers comprising cellulose, and include, but are not limited to,cotton, linen, flax, rayon, cellulose acetate, cellulose triacetate,hemp and ramie fibers. As used herein, “rayon fibers” is intended toinclude, but is not limited to, fibers comprising viscose rayon, highwet modulus rayon, cuprammonium rayon, saponified rayon, modal rayon andlyocell rayon. “Protein fibers”, are intended to refer to fiberscomprising proteins, and include, but are not limited to, wools, such assheep wool, alpaca, vicuna, mohair, cashmere, guanaco, camel and llama,and silks.

[0021] As used herein, “synthetic fibers” refer to those fibers whichare not prepared from naturally occurring filaments and include, but arenot limited to, fibers formed of synthetic materials such as polyesters,polyamides such as nylons, polyacrylics, and polyurethanes such asspandex. Synthetic fibers include fibers formed from petroleum products.As used herein, “synthetic elastic fibers” are those fibers which form“synthetic elastic yarns”, such as nontextured yams which can bestretched repeatedly at room temperature to at least twice theiroriginal length and which after removal of the tensile force willimmediately and forcibly return to approximately their original length.According to the present invention, synthetic elastic fibers include,but are not limited to, elastane fibers (i.e., Spandex). As is usedherein, “spandex” and “elastane” fibers both refer generally tomanufactured fibers in which the fiber forming substance is a long-chainsynthetic polymer comprised of at least 85% of a segmented polyurethane.

[0022] Elastic fabrics for use in the present invention comprise atextile product made from synthetic elastic fibers and/or syntheticelastic yams either alone or in combination with other textilematerials. Additionally, the elastic fabrics may be in the form ofgarments or other textiles comprising synthetic elastic fibers andnatural fibers. In one embodiment, the fabrics comprise at least about20% by weight of natural fibers, such as cotton fibers, rayon fibers orthe like. In additional embodiments, the fabrics comprise from about0.5% to about 20% by weight of synthetic elastic fibers.

[0023] While not being bound by theory, it is believed that when elasticfabrics containing natural fibers are treated with a compositioncomprising formaldehyde and a catalyst capable of cross-linkingformaldehyde with a natural fiber, a chemical modification of thenatural fibers occurs. It is believed that the formaldehyde reactschemically with the natural fibers to cross-link the individual polymerchains of the natural fibers, thereby improving various fabricperformance properties, such as for instance, durable press propertiesand/or dimensional stability, i.e., reduced dimensional change.Surprisingly, the elastic fabrics treated according to the presentmethods maintain their stretch performance properties, i.e., the fabricsremain elastic and exhibit good stretch recovery. This is surprising asone might expect that the crosslinking which provides improveddimensional stability and/or durable press would disadvantageously limitthe elasticity, and specifically the stretch ability and stretchrecovery properties, of the fabric. In accordance with the presentmethods, a silicone elastomer or precursor thereof may also be includedin the formaldehyde treatment to provide additional desirableproperties, for example good strength and/or tear strength, waterabsorbency and the like. The processes of the present invention are alsoadvantageous in providing fabrics exhibiting reduced drying time,improved fibrillation resistance and/or pill resistance and improvedbrightness.

[0024] To provide the crosslinked formaldehyde treatment, the fabric istreated with a treatment composition comprising formaldehyde and acatalyst followed by drying and/or curing of the treated fabric. In amore specific embodiment, the treatment composition further comprises asilicone elastomer or a precursor thereof. Formaldehyde is generallyavailable in an aqueous solution, referred to as formalin, comprisingwater, about 37% by weight formaldehyde, and generally about 10% to 15%by weight methanol. Formaldehyde may also be generated in an aqueoustreating solution in situ by adding paraformaldehyde (polyoxymethylene)to water, thereby generating formaldehyde.

[0025] The amount of formaldehyde in the treatment composition issufficient to impart improved dimensional stability and/or improveddurable press, while maintaining stretch recovery properties. In furtherembodiments, additional desirable properties are also provided. Theamount of formalin useful for imparting the above mentioned propertiesaccording to the present invention is typically dependent upon thecellulosic content of the fabric. In exemplary embodiments, the fabricis treated with at least about 1% by weight formalin, and specificallywith from about 2% to about 22% by weight formalin, based on the weightof the fabric. In one embodiment, for example wherein the fabriccomprises cotton fibers, the fabric is treated with about 5% to about 8%formalin, based on the weight of the fabric. In another embodiment, forexample wherein the fabric comprises rayon fibers, the fabric is treatedwith from about 12% to about 20% by weight formalin, based on the weightof the fabric. In yet another embodiment, for example wherein thenonelastic fibers in the fabric comprise a 50/50 rayon/polyester blend,the fabric is treated with from about 12% to about 20%, morespecifically about 16%, by weight formalin, based on the weight of thefabric. While “formalin” refers to an aqueous solution comprising 37%,by weight, formaldehyde, as will be apparent to one of skill in the art,formaldehyde solutions comprising levels of formaldehyde other than 37%,by weight, may also be used. Using the above ranges of formalin, thefabric is treated with actual formaldehyde, as opposed to formalin, at alevel of from about 0.5% to about 8%, specifically from about 1% toabout 7%, based on the weight of the fabric. Thus, in one embodiment,for example wherein the fabric comprises cotton fibers, the fabric istreated with about 1% to about 3% formaldehyde, as opposed to formalin,based on the weight of the fabric. In another embodiment, for examplewherein the fabric comprises rayon fibers, the fabric is treated withfrom about 5% to about 7% by weight formaldehyde, as opposed toformalin, based on the weight of the fabric. In yet another embodiment,wherein the nonelastic fibers in the fabric comprise a 50/50rayon/polyester blend, the fabric is treated with about 4% to about 7%by weight formaldehyde, as opposed to formalin, based on the weight ofthe fabric.

[0026] Suitable catalysts are those capable of catalyzing across-linking reaction between formaldehyde and a natural fiber, andspecifically are catalysts capable of catalyzing the cross-linking offormaldehyde with a natural fiber comprising hydroxy groups, such ascellulosic fibers. Catalysts which may be used include mineral acids,organic acids, salts of strong acids, ammonium salts, alkylamine salts,metallic salts and combinations thereof. In one embodiment the catalystis other than a mineral acid.

[0027] Suitable mineral acid catalysts include hydrochloric acid,sulfuric acid, nitric acid, phosphoric acid and boric acid. Suitableorganic acids include oxalic acid, tartaric acid, citric acid, malicacid, glycolic acid, methoxyacetic acid, chloroacetic acid, lactic acid,3-hydroxybutyric acid, methane sulfonic acid, ethane sulfonic acid,hydroxymethane sulfonic acid, benzene sulfonic acid, p-toluene sulfonicacid, cyclopentane tetracarboxylic acid, butane tetracarboxylic acid,tetrahydrofuran-tetracarboxylic acid, nitrilotriacetic acid, andethylenediaminetetraacetic acid. Suitable salts of strong acids includesodium bisulfate, sodium dihydrogen phosphate and disodium hydrogenphosphate. Suitable ammonium salts include ammonium chloride, ammoniumnitrate, ammonium sulfate, ammonium bisulfate, ammonium dihydrogenphosphate and diammonium hydrogen phosphate. Suitable alkanolamine saltsinclude the hydrochloride, nitrate, sulfate, phosphate and sulfamatesalts of 2-amino-2-methyl-l-propanol, tris (hydroxymethyl) aminomethaneand 2-amino-2-ethyl-1-3-propanediol. Suitable metal salts includealuminum chlorohydroxide, aluminum chloride, aluminum nitrate, aluminumsulfate, magnesium chloride, magnesium nitrate, magnesium sulfate, zincchloride, zinc nitrate and zinc sulfate, and mixtures thereof.

[0028] In one embodiment of the invention, the catalyst is a halide ornitrate salt of zinc or magnesium, and preferably the catalyst ismagnesium chloride. An organic acid, such as citric acid, may be used incombination with the halide or nitrate salt of zinc or magnesium.Generally the molar ratio of metal salt to organic acid is from about5:31 to about 20:1. In one embodiment, the catalyst comprises magnesiumchloride and citric acid, while in another embodiment the catalystcomprises magnesium chloride and aluminum chloride.

[0029] The fabric is typically treated with an amount of catalystsufficient to catalyze cross-linking of the natural fibers by theformaldehyde to provide improved dimensional stability and/or improveddurable press while maintaining stretch recovery properties. In oneembodiment, the catalyst may be employed in an amount sufficient toprovide a formaldehyde:catalyst weight ratio of from about 10:1 to about1:10, and specifically from about 5:1 to about 1:5.

[0030] The formaldehyde treatment composition may comprise, by weight,up to about 12% of a catalyst solution, and specifically from about 1%to about 9% of a catalyst solution. Generally the catalyst solutioncomprises from about 20% to about 50%, by weight catalyst. In oneembodiment, for example wherein the elastic fabric comprises cottonfibers, the treatment solution comprises from about 2 to about 4% byweight of a catalyst solution comprising about 30% by weight catalyst,and in another embodiment, for example wherein the elastic fabriccomprises rayon fibers, the treatment solution comprises from about 6%to about 8% by weight of a catalyst solution comprising about 30% byweight catalyst. In yet a further embodiment, the catalyst solutioncomprises about 40%, by weight, magnesium chloride, for a finalmagnesium chloride level of up to about 5%, by weight of the treatmentsolution. Suitable catalyst solutions include FREECAT® LF (magnesiumchloride and citric acid) and FREECAT® No. 9 (aluminum chloride andmagnesium chloride), commercially available from B. F. Goodrich.

[0031] The formaldehyde treatment composition typically comprises aliquid carrier, preferably water, although, as noted above, the formalinused to prepare the treatment composition may comprise small amounts oforganic solvents such as methanol or the like. In one embodiment, thetreatment composition is free of any organic solvents other than thatpresent in the formalin or the catalyst solution. In another embodiment,the carrier may comprise pentamethylcyclosiloxane.

[0032] According to exemplary embodiments of the present invention, asilicone elastomer or precursor thereof may be further included in theformaldehyde-containing treatment composition with which the fabric istreated. According to these embodiments, the formaldehyde treatmentcomposition comprises formaldehyde, catalyst and silicone elastomer or aprecursor thereof. The combination of a silicone elastomer or precursorthereof and the formaldehyde-containing treatment composition providesthe fabric with good strength and/or water absorbency, while alsoproviding good durable press and/or shrinkage resistance properties. Thegood water absorbency is remarkable in that many conventional durablepress and/or shrinkage resistance treatments render the treated fabricshydrophobic. The good strength is evident in a reduction of the loss intear and tensile strength that typically occurs during formaldehydecross-linking of fibers.

[0033] Various silicone elastomers are known in the art and are suitablefor use in the methods and fabrics of the invention. In one embodiment,the silicone elastomer is a polysiloxane. Similarly, the siliconeelastomer precursor which forms an elastomer upon curing, typically byself curing, may be a polysiloxane. Elastomers are polymers which arecapable of being stretched with relatively little applied force, andwhich return to the unstretched length when the force is released.Silicone elastomers have a backbone made of silicon and oxygen withorganic substituents attached to silicon atoms, with a number n ofrepeating units of the general formula:

[0034] The groups R and R′ are each independently selected from loweralkyls, preferably C₁-C₃ alkyls, phenyl, or lower alkyls or phenylscomprising a group reactive to cellulose, such as hydroxy groups,halogen atoms, for example, fluoride, or amino groups. Suitableelastomers include those disclosed in U.S. Pat. No. 5,885,303,incorporated herein by reference.

[0035] A preferred silicone elastomer or precursor composition comprisesup to about 60%, by weight, silicone solids. In one embodiment, thesilicone elastomer or precursor composition comprises from about 20% toabout 60%, specifically from about 30% to about 60%, by weight ofsilicone solids, while in another embodiment the silicone elastomer orprecursor composition comprises from about 20% to about 30% by weight ofsilicone solids. Suitable silicone elastomer precursors include adimethyl silicone emulsion containing from about 30% to about 60%, byweight, silicone solids, commercially available as SM2112 from GeneralElectric. Another suitable commercially available elastomer precursor isSedgesoft ELS from Sedgefield Specialties, containing from about 24% toabout 26%, by weight, silicone solids.

[0036] When the silicone elastomer or precursor thereof is applied tothe fabric with a liquid formaldehyde treatment composition, the liquidtreatment composition may comprise up to about 4%, specifically fromabout 0.1% to about 2.5%, more specifically from about 0.2% to about 2%,by weight of the elastomer or precursor solids. In one embodiment, thetreatment composition comprises from about 0.2% to about 2%,specifically from about 0.6% to 1.2%, by weight silicone solids, whilein another embodiment, the composition comprises from about 0.2% toabout 0.8% by weight silicone solids.

[0037] The formaldehyde treatment composition may be applied to thefabric in accordance with any of the conventional techniques known inthe art. In one embodiment, a liquid treatment composition may beapplied to the fabric by saturating the fabric in a trough and squeezingthe saturated fabric through pressure rollers to achieve a uniformapplication (padding process). As used herein “wet pick-up” refers tothe amount of treatment composition applied to and/or absorbed into thefabric based on the original weight of the fabric. “Original weight ofthe fabric” or simply “weight of the fabric” refers to the weight of thefabric prior to its contact with the treatment composition. For example,50% pick-up means that the fabric picks up an amount of treatmentsolution equal to 50% of the fabric's original weight. In specificembodiments, the wet pick-up is at least 20%, specifically from about50% to 100%, more specifically from about 65% to about 80%, by weight ofthe fabric.

[0038] Other application techniques which may be employed include kissroll application, engraved roll application, printing, foam finishing,vacuum extraction, spray application or any process known in the art.Generally these techniques provide lower wet pick-up than the paddingprocess. The concentration of the chemicals in the solution may beadjusted to provide the desired amount of chemicals on the originalweight of the fabric (OWF).

[0039] In a preferred embodiment, the formaldehyde treatment compositionis applied in an amount to insure a moisture content of more than 20% byweight, specifically more than 30% by weight, on the fabric beforecuring. Optionally, a wetting agent may be included in the treatmentcomposition to facilitate obtaining the desired moisture content.Nonionic wetting agents are preferred.

[0040] Once the treatment composition has been applied to the fabric,the fabric is typically heated for a time and at a temperaturesufficient for the cross-linking of the natural fibers with theformaldehyde. For example, the fabric may be heated at a temperaturegreater than about 250° F., specifically from about 250° F. to about375° F., in an oven for a period of from about 10 seconds to about 15minutes, specifically from about 45 seconds to about 3 minutes, to reactthe formaldehyde with the natural fibers in the fabric and affectcrosslinking of the formaldehyde and natural fibers to provide improveddimensional stability and maintained stretch recovery propertiestogether with effects such as, durable press and/or shrinkageresistance. There is an inverse relationship between curing temperatureand curing time, that is, the higher the temperature of curing, theshorter the dwell time in the oven; conversely, the lower the curingtemperature, the longer the dwell time in the oven. Additionally, theinventors of the present invention have unexpectedly discovered that thetreatment of the unique blend of synthetic elastic fibers and naturalfibers of the present fabrics minimizes up stream processing normallyincurred with relaxation, boil off and/or jamming procedures for elasticfabrics containing spandex/elastane fibers. As used herein,“relaxation”, “boil off”, and “jamming”, procedures each refer generallyto thermal processes which employ heat, moisture, and tension tomaximize the physical contraction of an elastic fiber. By minimizingsuch processing steps, the amount of time required wherein thetemperature is at or above about 120° F. is reduced. Additionally, thejamming process may be incorporated into the same procedure for thecrosslinking process. The single process flow procedure may then servefor multiple finishing operations i.e., jamming, crosslinking,formaldehyde removal, and heat setting. By consolidating these heattreating procedures, the life of the fabric may be increased. Withoutbeing bound by theory herein, the inventors therefore believe that theabovementioned desirable properties exhibited by the fabrics of thepresent invention are enhanced by the combination of both the chemicaland mechanical and/or procedural aspects of the processes disclosedherein.

[0041] In another embodiment, the present invention comprises methodsfor improving dimensional stability and/or durable press whilemaintaining stretch recovery properties of fabric, wherein the siliconeelastomer may be included in the treated fabric by means of a separatetreatment step before or after the formaldehyde crosslinking treatment.Additionally, if the silicone elastomer or precursor thereof is appliedto the fabric subsequent to treatment with the formaldehyde crosslinkingcomposition, the silicone elastomer precursor thereof may be appliedprior to or subsequent to the processing step which is employed toaffect curing of the formaldehyde with the natural fibers of the fabric,although in specific embodiments application prior to processing may bedesirable. The applied silicone elastomer or precursor thereof may bedried, with self curing of the precursor being affected thereby.

[0042] The fabrics according to the invention exhibit good durable pressproperties and/or good shrink resistance. In one embodiment, it ispreferred that the fabric exhibit good durable press, for example a DP(durable press) rating of at least about 3.0, specifically at leastabout 3.5, as measured according to AATCC Test Method 124-1996, afterone aqueous washing, more specifically after five aqueous washings,and/or good dimensional stability, for example a dimensional change inlength and width of less than about 5% each, specifically less thanabout 4.5% each, more specifically less than about 4.0% each, and incertain embodiments, less than about 3.0% each as measured according toAATCC Test Method 135-1995, after one machine washing, more specificallyafter five aqueous washings. Shrinkage resistance and/or dimensionalchange may also be measured according to AATCC Test Method 150-1995. Infurther embodiments, the fabrics exhibit good filling tensile and tearstrengths, for example of at least about 25 pounds and at least about 24ounces, respectively, as measured according to ASTM D-5035-95 fortensile strength, and ASTM D-2261-96 for tear strength.

[0043] The fabrics according to the invention also exhibit excellentsmoothness appearance and appearance retention with usage over time.Without being limited by theory herein, the present inventors believethat the unique combination of properties for formulating the elasticfabrics according to the present invention can be used to producefabrics with highly desirable feel and appearance properties, which havebeen otherwise unattainable by previously known methods. Moreparticularly, it has been discovered that elastic fabrics comprising ablend of synthetic elastic fibers and natural fibers, can be used toproduce garments that have excellent stretch/recovery properties whileminimizing unwanted fabric growth according to ASTM Test Method D3107;have minimal dimensional change over multiple washing cycles accordingto AATCC Test Method 135; have improved color appearance after multiplewashings as rated by the AATCC Gray Scale for Color Change; resistwrinkling to minimize the need for ironing according to ASTM Test MethodD2654; and dry in less time (i.e., about half the time of conventionalfabrics) to minimize the degradation of elastic fibers therein accordingto ASTM Test Method D2654.

[0044] Furthermore, such fabrics avoid the cost and complexity typicallyassociated with previous production methods, particularly during thepreparation, dyeing and finishing steps which are utilized to controljamming and/or the shrinkage of the fabrics. These production benefitsinclude, for instance, the elimination and/or reduction of heat setting,scouring and/or cool down processes typically found in previous fabricproduction techniques. Moreover, the processes of the present inventionproduce fabrics exhibiting reduced relaxation time, ply reduction andsectional slitting typically required by most fabrics during garmentmanufacturing, particularly as the sizing qualities of the fabrics areimproved through dimensional change reductions of cut pattern piecesduring garment production. Additionally, the fabrics have variouscutting room advantages such as, for instance, reduced conditioningtime, increased layering prior to cutting, improved tolerance for fabricsizing, the elimination of cutting sections for fabric relaxation andthe ability to utilize less fabric than traditionally needed duringproduction processes to make the garments. Moreover, and without beinglimited by theory herein, the inventors believe that fabrics treated viathe processes of the present invention will have improved fabrichandling characteristics during storage, as such fabrics exhibit reducedand/or eliminated bow and skew properties.

[0045] In a further embodiment, the fabrics according to the inventionexhibit good hand or softness, in the absence of conventional softenerssuch as silicone or polyethylene softeners. Typically, the fabrics willexhibit a low coefficient of friction and/or a high flexibility/Instronsoftness.

[0046] In processes in accordance with the present invention, unreactedformaldehyde remaining on the fabric is removed during subsequentprocessing of the fabric. Generally, the final substrate will compriseless than about 300 ppm formaldehyde, specifically less than about 200ppm formaldehyde, more specifically less than about 100 ppmformaldehyde, and even more specifically less than about 50 ppmformaldehyde, as measured according to AATCC Test Method 112-1993.

[0047] Some polysiloxanes, generally referred to as silicone oils, havea liquid form, are not elastomeric and do not self-crosslink. Siliconeoils include, for example, non-reactive linear polydimethyl siloxanes,that is, siloxanes which are not capable of further reaction with othersilicones and are not capable of a self curing reaction. Silicone oilshave a tendency to produce non-removable spots on fabrics. In contrast,the silicone elastomers used in the present invention generally do notproduce such spots. Although the fabrics or treatment compositions maycomprise silicone oil, in one embodiment, the fabrics and treatmentcompositions are substantially free of, and specifically are free of,silicone oil. As used herein, substantially free of silicone oils meansthe treatment compositions and fabrics comprise less than 1%, by weight,silicone oil.

[0048] Thermosetting resins used to impart durable press properties tofabrics are generally aminoplast resins which are the products of thereaction of formaldehyde with compounds such as urea, thiourea, ethyleneurea, dihydroxyethylene urea and melamines. As used herein “aminoplastresins” is intended to include N-methylolamide cross-linking agents suchas dimethylol dihydroxyethylene urea, dimethylol urea,dimethylolethylene urea, dimethylol propylene urea, dimethylol methylcarbamate, dimethylol n-propylcarbamate, dimethylol isopropylcarbamatetrimethylolated melamine, and tris(methoxymethol) melamine.Specifically, the fabrics, methods and formaldehyde treatmentcompositions of the invention are substantially free of, and morespecifically are free of, aminoplast resins and N-methylol cross-linkingagents. As used herein, “substantially free” of aminoplast resins andN-methylol cross-linking agents is intended to mean the fabrics andtreatment solutions comprise less than about 0.5%, by weight, aminoplastresin or methylol cross-linking agent.

[0049] Prior to treatment with the formaldehyde composition and siliconeelastomer or precursor thereof, the fabric may optionally be preparedusing any fiber, yarn, or textile pre-treatment preparation techniquesknown in the art. Suitable preparation techniques include brushing,singeing, desizing, scouring, mercerizing, and bleaching. For example,fabric may be treated by brushing which refers to the use of mechanicalmeans for raising surface fibers which will be removed during singeing.The fabric may be then be singed using a flame to bum away fibers andfuzz protruding from the fabric surface. Textiles may be desized, whichrefers to the removal of sizing chemicals such as starch and/orpolyvinyl alcohol, that are put on yarns prior to weaving to protectindividual yarns. The fabrics may be scoured, which refers to theprocess of removing natural impurities such as oils, fats and waxes andsynthetic impurities such as mill grease from fabrics. Mercerizationrefers to the application of high concentrations of sodium hydroxide toa fabric to alter the morphology of fibers, particularly cotton fibers.Fabrics may be mercerized to improve fabric stability and luster.Finally, bleaching refers to the process of destroying any natural colorbodies within the natural fiber. A typical bleaching agent is hydrogenperoxide.

[0050] The various preparation techniques are optional and dependentupon the desired final product. For example, when the final fabric is tobe dyed a dark color, there may be no need to bleach the substrate.Similarly, there may be no need to desize a knit which was preparedwithout using any sizing agents, and no need to separately scour knitsand woven textiles as the scouring may be done during bleaching.

[0051] The following examples are set forth to demonstrate the methodsof the present invention and the improved dimensional stability and/ordurable press properties together with maintained stretch recoveryproperties which are obtained in elastic fabrics by the methods of thepresent invention. Throughout the examples and the presentspecification, parts and percentages are by weight unless otherwisespecified. The following examples are illustrative only and are notintended to limit the scope of the methods and fabrics of the inventionas defined by the claims.

EXAMPLE 1

[0052] In this example, elastic fabric samples are provided with aformaldehyde crosslinking treatment in accordance with the invention.According to this example, an elastic fabric comprising 97% rayon and 3%spandex is treated with from about 15% to about 22% by weight offormalin (37% formaldehyde), from about 3% to about 6% of a catalystsolution, and from about 0.1% to about 1.5% of silicone elastomersolids.

EXAMPLE 2

[0053] In this example, elastic fabric samples are provided with aformaldehyde crosslinking treatment in accordance with the invention.According to this example, an elastic fabric comprising 65% cotton, 32%rayon and 3% spandex, is treated with from about 15% to about 18% byweight of formalin (37% formaldehyde), about 3% of a catalyst solution,and about 1% silicone elastomer solids.

[0054] The examples and specific embodiments set forth herein are forillustrative purposes only and are not intended to limit the scope ofthe methods and fabrics of the invention Additional methods and fabricswithin the scope of the claimed invention will be apparent to one ofordinary skill in the art in view of the teachings set forth herein.

What is claimed is:
 1. A method for providing elastic fabric comprisingsynthetic elastic fibers and natural fibers with improved dimensionalstability while maintaining stretch recovery properties of the fabric,comprising treating elastic fabric comprising synthetic elastic fibersand natural fibers with a treatment composition comprising formaldehydeand a catalyst for crosslinking the formaldehyde with the natural fibersin the fabric, and processing the treated fabric to effect crosslinkingof the formaldehyde and to maintain stretch performance properties.
 2. Amethod according to claim 1, wherein the treatment composition furthercomprises a silicone elastomer or a precursor thereof.
 3. A methodaccording to claim 2, wherein the fabric comprises from about 0.5% toabout 20% by weight of the synthetic elastic fibers.
 4. A methodaccording to claim 2, wherein the synthetic elastic fibers comprise atleast about 85% of a segmented polyurethane.
 5. A method according toclaim 2, wherein the fabric comprises at least about 20% by weight ofthe natural fibers.
 6. A method according to claim 2, wherein thenatural fibers comprise cellulosic fibers selected from the groupconsisting of cotton, linen, flax, rayon, cellulose acetate, cellulosetriacetate, hemp and ramie fibers.
 7. A method according to claim 2,wherein the treatment composition is free of aminoplast resin.
 8. Amethod according to claim 2, wherein the resulting fabric exhibits alength dimensional change and a width dimensional change of less thanabout 5% each after the fabric has been aqueous laundered one time.
 9. Amethod according to claim 2, wherein the resulting fabric exhibits afabric growth of not greater than about 5% after the fabric has beenstretched at least about 80%.
 10. A method for providing elastic fabriccomprising synthetic elastic fibers and natural fibers with improveddurable press while maintaining stretch recovery properties of thefabric, comprising treating elastic fabric comprising synthetic elasticfibers and natural fibers with a treatment composition comprisingformaldehyde and a catalyst for crosslinking the formaldehyde with thenatural fibers in the fabric, and processing the treated fabric toeffect crosslinking of the formaldehyde and to maintain stretchperformance properties.
 11. A method according to claim 10, wherein thetreatment composition further comprises a silicone elastomer or aprecursor thereof.
 12. A method according to claim 11, wherein thefabric comprises from about 0.5% to about 20% by weight of the syntheticelastic fibers.
 13. A method according to claim 11, wherein thesynthetic elastic fibers comprise at least about 85% of a segmentedpolyurethane.
 14. A method according to claim 11, wherein the fabriccomprises at least about 20% by weight of the natural fibers.
 15. Amethod according to claim 11, wherein the natural fibers comprisecellulosic fibers selected from the group consisting of cotton, linen,flax, rayon, cellulose acetate, cellulose triacetate, hemp and ramiefibers.
 16. A method according to claim 11, wherein the treatmentcomposition is free of aminoplast resin.
 17. A method according to claim11, wherein the resulting fabric exhibits a durable press value of atleast about 3.0 after the fabric has been aqueous laundered one time.18. A method according to claim 11, wherein the resulting fabricexhibits a fabric growth of not greater than about 5% after the fabrichas been stretched at least about 80%.
 19. Fabric comprising syntheticelastic fibers and natural fibers and exhibiting a durable press valueof at least about 3.0 after the fabric has been aqueous laundered onetime.
 20. Fabric according to claim 19, wherein the fabric exhibits afabric growth of not greater than about 5% after the fabric has beenstretched at least about 80%.
 21. Fabric comprising synthetic elasticfibers and natural fibers and exhibiting a length dimensional change anda width dimensional change of less than about 5% each after the fabrichas been aqueous laundered one time.
 22. Fabric according to claim 21,wherein the fabric exhibits a fabric growth of not greater than about 5%after the fabric has been stretched at least about 80%.